Recently, development of an electroluminescent device (organic electroluminescence element) using an organic material in place of an inorganic material such as ZnS is proceeding. For achieving high efficiency and long life of the electroluminescent device, a hole transport layer is generally provided between an anode and a light emitting layer.
A polymer having a repeating unit represented by the following formula (1) is disclosed in Patent Documents 1 and 2, and an organic electroluminescence element using, for the hole injection layer, a polymer having a repeating unit represented by formula (1) is proposed in Patent Document 3. However, the organic electroluminescence element described in this patent document has a high drive voltage and fails in obtaining sufficiently high luminous efficiency.
(wherein each of Ar1 and Ar2 independently represents an aromatic hydrocarbon group which may have a substituent, or an aromatic heterocyclic group which may have a substituent).
Also, Patent Documents 4 and 5 each discloses a polymer compound having repeating units represented by the following formulae, but when a device is produced using such a compound, this incurs a problem that a flat film is not obtained or the drive life of the obtained device is short.

Furthermore, Patent Document 6 discloses a polymer compound having a repeating unit represented by the following formula, but when a device is produced using such a compound, this causes a problem that the charge transporting ability is low and the drive voltage of the obtained device is high.

Patent Document 1: U.S. Pat. No. 6,034,206
Patent Document 2: JP-A-2005-285749 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”)
Patent Document 3: International Publication No. 2004/014985, pamphlet
Patent Document 4: International Publication No. 2008/038747, pamphlet
Patent Document 5: International Publication No. 2005/053056, pamphlet
Patent Document 6: International Publication No. 2002/010129, pamphlet